Children (age 0-14 years) with congenital lacrimal stenosis in whom probing and intubation of the lacrimal drainage system is indicated are included the study after informed written consent by their parents. Microbiological specimens are taken bilaterally from conjunctiva and nasal mucosa during the two procedures under general anaesthesia (insertion and removal of the silicon intubation) and from the silicon tube after removal. Specimens are examined for bacterial contamination. Microbiological findings are correlated with clinical data about the further clinical course and especially the success of the surgical treatment.